As used in connection with the present application, the expression "Y-piece" also includes shapes other than that of conventional "Y." Of significance is only the fact that the patient attachment piece can be connected to an inhalation and exhalation tube, respectively. The expression "Y-piece" thus also includes, for example, T-connectors and connectors for coaxially connecting arranged inhalation and exhalation tubes.
In addition, the term "patient attachment piece" is also used in connection with this application. The "patient attachment piece" is intended to be attached to the portion of the Y-piece which is directed towards the patient. These patient attachment pieces can, for example, be designed in accordance with U.S. Pat. No. 4,516,573. In this patent there is thus described a bellowed patient attachment piece, which contains a wad of moisture- and heat-absorbing material. In this manner, heat and moisture are taken up from the exhaled gas and provided to the inhaled gas. Such patient attachment pieces are often connected with various types of Y-pieces and may be equipped with various types of bacterial filters. The more components which are connected, however, lead to a bulkier construction, which can thus become rather inconvenient for the patient. Furthermore, the connection of a number of different components creates the risk of both leakage and, on the other hand, improperly connected components.
When a patient is attached to a respirator, anesthesia machine or the like, there also arises a need for continuous or intermittent sampling of the exhaled gas and for proximal pressure measuring. This should take place as close to the patient as possible, and can occur, for example, in the manner described in U.S. Pat. No. 4,838,258; i.e., by means of a tube which extends from the respirator itself, through the exhalation tube, to a point near the patient. The disadvantage with this construction, however, is that the withdrawn sample can be, on the one hand, extremely moist, and, on the other hand, contaminated with bacteria.
Furthermore, in the case of conventional Y-pieces, a certain dead volume must be taken into account. By dead volume is meant the quantity of exhaled gases which return to the patient. This dead volume rapidly increases if the Y-piece is provided with extra functions, such as with a bacteria filter, as described, for example, in Swedish Patent Application No. 90.02162/7, filed Jun. 18, 1990.